This invention relates generally to devices for sensing the condition of an electrical apparatus and providing an indicia of the sensed condition. More specifically, the present invention relates to a system for detecting the condition of a lamp and activating a permanent memory two-state display of the lamp condition.
Maintenance crews assigned the task of maintaining street lights in good working order have experienced difficulties in determining whether or not the lamp of the street light is in good working order. The problem is manifest in the fact that the maintenance crews are typically employed during daylight hours to maintain the street lights, when they are typically turned off.
Most street lights are controlled by a timer or a photoelectric cell so that the lamps are illuminated during twilight and nighttime hours, and turned off during the day time to conserve electrical power. Often maintenance crews have been forced to rely on reports from the general public that a particular street lamp is defective, which lamp is often difficult to locate by the maintenance crew after the report is filed. An alternative approach to maintaining street lights has been to periodically change all of the lamps during normal working hours, irrespective of the condition of any particular lamp. This approach, which has been adopted primarily in view of the absence of a reliable system for informing maintenance crews of lamp condition during day time hours, is inherently expensive since lamps are being replaced which are of good working order.
Accordingly, there has been a need for a system which is activated only when the lamp is supposed to be lighted, for detecting the condition of the lamp and activating a permanent memory two-state display of the lamp condition which can then be monitored by maintenance crews during day time hours. Such a system should be easily installed, energy efficient and highly reliable. Further, such a detection and display system is needed which is energized by the power lines connected to the lamp, and yet may be electrically isolated from those power lines if desired. Such a system would preferably transform alternating current of power lines into a direct current for powering the system, and permit accurate detection of the lamp condition. The present invention fulfills these needs and provides other related advantages.